Sound: how it is made, travels and changes

Sound comes from vibration

Every sound starts with something vibrating: a guitar string, a drum skin, the air in a flute, our vocal cords. Stop the vibration and the sound stops instantly — touching a ringing bell proves it.

Sound needs a material to travel through

Vibrations pass through solids, liquids and gases, but not through a vacuum. Sound travels fastest in solids because their particles are closest together and pass the vibration on quickest.

Loudness and pitch are different

Loudness depends on how big the vibration is: hit the drum harder, get a louder sound. Pitch depends on how fast it vibrates: a shorter, tighter or thinner string vibrates faster and gives a higher pitch. Mixing these two up is the commonest error in this topic.

Getting quieter with distance

Sound spreads out as it travels, so it gets quieter the further you are from the source.